A kinetic mechanism for the fast movement of Chara myosin

Yuji Kimura, Nobutada Toyoshima, Noboru Hirakawa, Keiichirou Okamoto, Akihiko Ishijima

Research output: Contribution to journalArticlepeer-review

38 Citations (Scopus)


Endoplasmic streaming of characean cells of Nitella or Chara is known to be in the range 30-100μm/second. The Chara myosin extracted from the cells and fixed onto a glass surface was found to move muscle actin filaments at a velocity of 60μm/second. This is ten times faster than that of skeletal muscle myosin (myosin II). In this study, the displacement caused by single Chara myosin molecules was measured using optical trapping nanometry. The step size of Chara myosin was approximately 19nm. This step size is longer than that of skeletal muscle myosin but shorter than that of myosin V. The dwell time of the steps was relatively long, and this most likely resulted from two rate-limiting steps, the dissociation of ADP and the binding of ATP. The rate of ADP release from Chara myosin after the completion of the force-generation step was similar to that of myosin V, but was considerably slower than that of skeletal muscle myosin. The 19nm step size and the dwell time obtained could not explain the fast movement. The fast movement could be explained by the load-dependent release of ADP. As the load imposed on the myosin decreased, the rate of ADP release increased. We propose that the interaction of Chara myosin with an actin filament resulted in a negative load being imposed on other myosin molecules interacting with the same actin filament. This resulted in an accelerated release of ADP and the fast sliding movement.

Original languageEnglish
Pages (from-to)939-950
Number of pages12
JournalJournal of Molecular Biology
Issue number4
Publication statusPublished - 2003 May 9
Externally publishedYes


  • Chara corallina
  • Chara myosin
  • Load dependence
  • Optical trapping nanometry
  • Single molecule mechanochemistry

ASJC Scopus subject areas

  • Structural Biology
  • Molecular Biology


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